Dielectric resonator antennas (DRA) are known as miniaturized antennas of ceramics or another dielectric medium for microwave frequencies. In a dielectric resonator whose dielectric medium .di-elect cons..sub.r &gt;&gt;1 is surrounded by air, this dielectric medium has a discrete spectrum of self-frequencies and self-modes. Contrary to a resonator, which has a very high quality when radiation losses are avoided, the radiation of power is in the forefront in the resonator antenna. Since no conducting structures are used as a radiating element, the skin effect can have no detrimental consequences. Therefore, such antennas have low-ohmic losses at high frequencies. When materials having a high dielectric constant are used, furthermore a compact, miniaturized structure may be achieved. FIG. 1 shows such a DR antenna 1 in the basic form regarded as an example. In addition to the form of a parallelepiped, also other forms are possible, such as for example, cylindrical or spherical geometries. Dielectric resonator antennas are resonant elements which operate only in a narrow band around one of the their resonant frequencies. The problem of the miniaturization of an antenna is equivalent to lowering the operating frequency with given antenna dimensions. As a result, the lowest resonance (TE.sup.z.sub.111 -mode) is used. This mode has a plane, which is called plane of symmetry 2, in which the tangential component of the electric field disappears. When the antenna is halved in the plane of symmetry 2 and an electrically conducting surface 3 is deposited (for example, a metal plate), the resonant frequency continues to be equal to the resonant frequency of an antenna having the original dimensions. This is represented in FIG. 2. A further miniaturization with this antenna can be achieved by means of a dielectric medium having a high dielectric constant .di-elect cons..sub.r. For this purpose, preferably a material having minor dielectric losses is chosen.
Such a dielectric resonator antenna is described in the article "Dielectric Resonator Antennas--A review and general design relations for resonant frequency and bandwidth", Rajesh K. Mongia and Prakash Barthia, Intern. Journal of Microwave and Millimeter-Wave Computer-aided Engineering, vol. 4, no. 3, 1994, pp. 230-247. The article gives an overview of the modes and radiation characteristic for various shapes, such as cylindrical, spherical and rectangular DRAs. For different shapes the possible modes and planes of symmetry are shown (see FIGS. 4, 5, 6 and page 240, left column, lines 1-21). Particularly a parallelepiped-shaped dielectric resonator antenna is described in the FIG. 9 and the associated description. By means of a metal surface in the x-z plane with y=0, or in the y-z plane with x=0, the original structure may be halved without modifying the field distribution or other resonance characteristics for the TE.sup.z.sub.111 -mode (page 244, right column, lines 1-7). The DRA is excited via a microwave transmission line in that it is inserted into the stray field in the neighborhood of a microwave line (for example, a microstrip line or the end of a coaxial line).
With this type of coupling of the power, the impedance matching of the dielectric resonator antenna with the transmission line, necessary for a good efficiency, is hard, because the matching strongly depends on the position of the antenna relative to the transmission line. The deviation of the relative position of the transmission line, however, strongly varies especially in the case of automatic production.